现有大量临床及实验材料证明

尾核、丘脑的束旁核、三叉神经脊束核、脊髓背角等核团与针刺镇痛有密切关系。据我们观察

这些核团都接受大脑皮质的传出纤维

即在大脑皮质与核团间存在着直接的下We have made experiments in rats to trace descending nervefibral connections between the cerebral cortex and certain nuclear masses responsible for painful sensation and expected to provide some morphological evidence for studying the mechanism of acupuncture anesthesia. Experiments were carried out On 13 rats. Damage was induced individually to various cortical areas(somato-motor

somato-sensory

auditory and visual areas). The corticofugal fibers terminating into nuclear masses responsible for pain sensation were traced in sections by means of the Nauta-Gygex method. 1. Degenerated corticofugal fibers entering the ipsilateral N. caudatus could be traced in all slides taken from brain sections of the 13 rats with different damaged cortical areas. Preterminal degenerated fibers were distributed aroud the cells in the dorsal-external part of the caput of the N. caudatus. There were no or only scanty degenerated fibers found at the ventral-internal part of the caput of the N. caudatus and the caudal part of the nucleus. What we have found in our experiment is in accordance with clinical practice and demonstrated in physiological experiments

that the dorsal part of the caput of the N. caudatus is the reacting center of electric acupuncture analgesia. The direct connection between the cortex and N. caudatus is a possible anatomic basis for transmitting cortical influences to the nucleus. 2. On sections of the brain with damaged somato-motor and somatosensory areas

preterminal degenerating fibers can be found in the thalamic N. parafascicularis. This means that the above mentioned nucleus directly receives the cortical projecting fibers. As confirmed by electrophysiologic studies

the N. parafascicularis is a structure closely associated with pain sensation or analgesia. The direct projecting fibers may be the pathway by which cortical inhibitory influences are transmitted to the N. parafascicularis. 3. Degenerated corticofugal fibers from the damaged somato-motor

somato-sensory and auditory areas can be demonstrated in all stained brain slides. These degenerated fibers project into the spinal trigeminal nucelus mostly on the opposite sides. The direct convergence of the corticofugal fibers with the trigeminal fibers of first order is suggetted to be the ana tomic basis to explain how the cortex exerts efferent inhibitory action through the pyramidal tract uppon the afferent pain impulses initiated from the cephalic-facial origin. 4. On cross-sections of the spinal cord in rets with damaged somatomotor and somato-sensory areas

the degenerated cortico-spinaltract is located ventrally to the opposite spinal dorsal fasciculus. With the fasciculus as a center

the degenerated fibers spread in a radiating mode toward the spinal dorsal cornu and the intermediate area. Preterminal degenerated fibers are also found around the cells in the vicinity of the nucleus proprius cornu dorsalis

basis cornu dorsalis and intermediate area. Cells in the spinal dorsal cornu are the primary centers admitting afferent pain impulses from the body and extremities. The cortico-spinaltract may be considered as the anatomic basis for cortical efferent impulses acting on spinal dorsal cornu to exert inhibitory influences on the transmition of integration of pain signals.